Continuous crown reinforcement for a pneumatic tire

ABSTRACT

A pneumatic tire includes a carcass reinforced by a carcass ply extending from a first bead to a second bead, and a single reinforcement disposed radially outward of the carcass ply in a crown portion of the pneumatic tire. The single reinforcement includes a continuous cord forming a generally zig zag pattern across the width of the crown portion. The continuous cord is part of a continuous strip with a constant width of 3.0 mm to 30.0 mm.

FIELD OF THE INVENTION

The present invention relates to a pneumatic tire, and more particularly, to a belt construction for a pneumatic tire.

BACKGROUND OF THE INVENTION

A pneumatic tire typically includes a pair of axially separated inextensible beads. A circumferentially disposed bead filler apex extends radially outward from each respective bead. At least one carcass ply extends between the two beads. The carcass ply has axially opposite end portions, each of which is turned up around a respective bead and secured thereto. Tread rubber and sidewall rubber is located axially and radially outward, respectively, of the carcass ply. A belt structure is disposed radially between the carcass ply and tread rubber.

The bead area is one part of the tire that contributes a substantial amount to the rolling resistance of the tire, due to cyclical flexure which also leads to heat buildup. Under conditions of severe operation, as with runflat and high performance tires, the flexure and heating in the bead region can be especially problematic, leading to separation of mutually adjacent components that have disparate properties, such as the respective moduli of elasticity. In particular, the ply turnup ends may be prone to separation from adjacent structural elements of the tire.

A conventional ply may be reinforced with materials such as polyamide/nylon, polyester, rayon, and/or metal, which have much greater stiffness (i.e., modulus of elasticity) than the adjacent rubber compounds of which the bulk of the tire is made. The difference in elastic modulus of mutually adjacent tire elements may lead to separation when the tire is stressed and deformed during use.

A conventional belt structure comprises a plurality of reinforcement layers in which cords are laid parallel to each other. Due to the unidirectional load carrying capability of each reinforcement layer, an even number of such layers may be stacked up to manage the force transfer in opposite directions. Two such reinforcement layers of steel wires may be used as a belt-package in a typical radial passenger tire, contributing significant weight to the pneumatic tire.

SUMMARY OF THE INVENTION

A pneumatic tire in accordance with the present invention includes a carcass reinforced by a carcass ply extending from a first bead to a second bead, and a single reinforcement disposed radially outward of the carcass ply in a crown portion of the pneumatic tire, the single reinforcement comprising a continuous cord forming a generally zig zag pattern across the width of the crown portion, the continuous cord being part of a continuous strip with a constant width of 3.0 mm to 30.0 mm.

According to another aspect of the pneumatic tire, the continuous cord has a 2×0.295 high tensile steel construction.

According to still another aspect of the pneumatic tire, the continuous cord has a 2+2×0.22 ultra tensile steel construction.

According to yet another aspect of the pneumatic tire, the continuous cord is part of a group of cords of identical construction.

According to still another aspect of the pneumatic tire, the continuous cord comprises carbon fiber.

According to yet another aspect of the pneumatic tire, the continuous cord comprises polyester.

According to still another aspect of the pneumatic tire, the continuous cord comprises polyamide.

According to yet another aspect of the pneumatic tire, the continuous cord comprises aramid.

According to still another aspect of the pneumatic tire, the continuous cord comprises fused polyester.

A method in accordance with the present invention designs a pneumatic tire. The method includes the steps of: replacing a first belt, a second belt, and an overlay with a single continuous reinforcement, the single continuous reinforcement comprising the continuous cord being part of a continuous strip with a constant width of 3.0 mm to 30.0 mm.

DEFINITIONS

“Apex” or “bead filler apex” means an elastomeric filler located radially above the bead core and between the plies and the turnup plies.

“Axial” and “Axially” mean the lines or directions that are parallel to the axis of rotation of the tire.

“Bead” or “Bead Core” generally means that part of the tire comprising an annular tensile member of radially inner beads that are associated with holding the tire to the rim; the beads being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers.

“Carcass” means the tire structure apart from the belt structure, tread, undertread over the plies, but including the beads.

“Casing” means the carcass, belt structure, beads, sidewalls and all other components of the tire excepting the tread and undertread, i.e., the whole tire.

“Chipper” refers to a narrow band of fabric or steel cords located in the bead area whose function is to reinforce the bead area and stabilize the radially inwardmost part of the sidewall.

“Circumferential” most often means circular lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction; it can also refer to the direction of the sets of adjacent circular curves whose radii define the axial curvature of the tread, as viewed in cross section.

“Cord” means one of the reinforcement strands, including fibers, with which the plies and belts are reinforced.

“Equatorial Plane” means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread; or the plane containing the circumferential centerline of the tread.

“Flipper” refers to a reinforcing fabric around the bead wire for strength and to tie the bead wire in the tire body.

“Gauge” refers generally to a measurement and specifically to thickness.

“Inner Liner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire.

“Lateral” means a direction parallel to the axial direction.

“Normal Load” means the specific design inflation pressure and load assigned by the appropriate standards organization for the service condition for the tire.

“Ply” means a cord-reinforced layer of rubber-coated radially deployed or otherwise parallel cords.

“Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire.

“Radial Ply Structure” means the one or more carcass plies or which at least one ply has reinforcing cords oriented at an angle of between 65° and 90° with respect to the equatorial plane of the tire.

“Radial Ply Tire” means a belted or circumferentially-restricted pneumatic tire in which at least one ply has cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire.

“Section Height” means the radial distance from the nominal rim diameter to the outer diameter of the tire at its equatorial plane.

“Section Width” means the maximum linear distance parallel to the axis of the tire and between the exterior of its sidewalls when and after it has been inflated at normal pressure for 24 hours, but unloaded, excluding elevations of the sidewalls due to labeling, decoration or protective bands.

“Sidewall” means that portion of a tire between the tread and the bead.

“Toe guard” refers to the circumferentially deployed elastomeric rim-contacting portion of the tire axially inward of each bead.

“Tread width” means the arc length of the tread surface in the plane includes the axis of rotation of the tire.

“Turnup end” means the portion of a carcass ply that turns upward (i.e., radially outward) from the beads about which the ply is wrapped.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure, operation, and advantages of the invention will become more apparent upon contemplation of the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 represents a schematic cross-sectional view of an example tire for use with the present invention;

FIG. 2 represents a schematic detail view of the bead region of the example tire shown in FIG. 1;

FIG. 3 represents a schematic detail view of a crown reinforcement in accordance with the present invention;

FIG. 4 represents a schematic detail view of another crown reinforcement in accordance with the present invention.

DETAILED DESCRIPTION OF EXAMPLES OF THE PRESENT INVENTION

FIGS. 1 and 2 show an example tire 10 for use with reinforcing structures, such as flippers and chippers, in accordance with the present invention. The example tire 10 has a tread 12, an inner liner 23, a belt structure comprising belts 18, 20, an overlay 16, a carcass 22 with a single carcass ply 14, two sidewalls 15,17, and two bead regions 24 a, 24 b comprising bead filler apexes 26 a, 26 b and beads 28 a, 28 b. The example tire 10 is suitable, for example, for mounting on a rim of a passenger vehicle. The carcass ply 14 includes a pair of axially opposite end portions 30 a, 30 b, each of which is secured to a respective one of the beads 28 a, 28 b. Each axial end portion 30 a or 30 b of the carcass ply 14 is turned up and around the respective bead 28 a, 28 b to a position sufficient to anchor each axial end portion 30 a, 30 b, as seen in detail in FIG. 2.

The carcass ply 14 may be a rubberized ply having a plurality of substantially parallel carcass reinforcing members made of such material as polyester, rayon, or similar suitable organic polymeric compounds. The carcass ply 14 may engage the axial outer surfaces of two flippers 32 a, 32 b.

In accordance with the present invention, the overlay 16 and belts 18, 20 may be replaced with a single crown reinforcement 301 (FIG. 3). The reinforcement 301 may be made of a spirally wound continuous strip 303 in a zig zag pattern in two or more layers. The strip 303 may have a width between 3.0 mm-30.0 mm and may be comprised of rubber reinforced with one or more cords 305 having an elongation at break of less than 2.5%. Conventional strips are reinforced with cords having an elongation to break of greater than 3.5%, greater than 4%, or greater than 4.5%.

Conventional high-speed passenger tires may have a spirally wound overlay reinforcement radially outward of a belt structure. The crown reinforcement 301 may allow removal of the overlay while the pneumatic tire 10 still functions suitably at high speeds. Removing the overlay may reduce material cost, tire weight, and flat spotting. The elimination of cut belt edges may also mitigate belt edge separation and provide improved crown durability.

The crown reinforcement 301 may be constructed using 1-5 periods of sinusoidal wrap per revolution providing cord/tape angles between 20-40 degrees, or between 25-35 degrees to provide sufficient cornering stiffness. The cords of the crown reinforcement 301 may be steel, PET, polyamide, aramid, hybrid combinations, and/or fused polyester cord, such as that described in US 2013/0240106, herein incorporated by reference in its entirety. For example, the cords may have a 2×0.295 high tensile steel and/or a 2+2×0.22 ultra tensile steel construction. Utilizing combinations of different materials may also provide unique advantages particularly for weight and thermal conductivity. For example, the strength of steel reinforcements may be combined with aramid or fiber glass to reduce weight and maintain stiffness and strength. Carbon fiber may be added to increase thermal conductivity of the reinforcement 301 to increase high speed performance by conducting heat away from hot spots.

As stated above, the continuous strip crown reinforcement 301 may replace a conventional structure of two steel belts 18, 20 and an overlay 16, for example, for passenger and radial light truck tires. This could lead to a current cost savings of 1.5 USD to 3 USD per tire, improved durability, and more flexible manufacturing.

The strip 303 may be reinforced with steel, steel textile, and/or hybrid cords and/or monofilaments. This reinforcement 301 may further eliminate belt stock preparation steps and provide increased flexibility choosing reinforcement materials. Elimination of the overlay 16 may reduce tire weight, flat spotting, and cost. Also, elimination of cut belt edges may increase high speed performance and durability by removing belt edge crack initiation sites. Since this reinforcement 301 may provide suitable stiffness and strength to a consumer tire, then high speed, plunger, durability, and ride and handling requirements may also be met or exceeded. This reinforcement 301 may further produce increasing rolling resistance by implementing alternative methods to improve tack during the zig-zag application process.

The endless reinforcement 301 of the present invention may have a generally cylindrical form or configuration and may be made from fiber glass, rayon, polyester, nylon, cotton, aramid, metal wire, etc. The dimensions may be varied over a considerable range depending upon the desired parameters of the tire 10.

The reinforcement 301 may be formed from a minimum number of cords so that the number of cut ends will be negligible. The complete reinforcement 301 may be formed from a single cord which forms the generally zigzag pattern. In this case, the two ends of the single cord may be the only cut ends in the reinforcement. Under some conditions, it may be desirable to form the reinforcement 301 from several cords simultaneously with each of the cords being in the same zigzag pattern and being positioned similarly to the single cord, but displaced therefrom. This may facilitate the production of the reinforcement 301 in a short period of time. Thus, the reinforcement 301 of the present invention may be an endless strip minimizing splices, which may lead to imbalance and possible premature failure of the tire 10.

The cord in the zigzag pattern may be positioned across the width of the reinforcement 301 from one side to the other at an angle to the edges. The initial angle of the cord may be in the range of 45° to 80° or 50° to 70° as measured from an edge. During expansion of such a reinforcement 301, the angle of the cord may be reduced to an angle in the range of 5° to 35°. With a reinforcement 301 applied on to a carcass 14 after the carcass has been expanded, the angle of the cord may generally be in the range of 10° to 35°, or about the same angle as the final cord angle of an expanded reinforcement. Also, the angle of the cord may change across the width thereof. As a result, the angle of the cord in the portions thereof adjacent to the edges may be greater or less than the angle of the cord in the center portion. Such a construction may be advantageous where different reinforcement expansion characteristics are desired for particular shapes or types of tires.

The reinforcement 301 may define a reversal of the cord at the edges. Upon this reversal, the succeeding length of cord may be positioned in the zigzag pattern at approximately the same angle with respect to one edge as the previous length of cord prior to the reversal with respect to the opposite edge. This may provide a symmetrical cord position in the final construction and minimize imbalance in the tire 10.

The edges of the reinforcement 301 may be staggered with respect to other reversal points. Thus, the point of reversal for a given length of cord may be closer to the center than an average, or farther away, as desired. Such staggering of the reversal points may provide a reinforcement 301 with edges somewhat thinner than the main body of the reinforcement.

Lengths of cord between reversals in the reinforcement 301 may be interleaved with lengths disposed at an opposite angle. This interleaving of the cord may be along a line or zone substantially parallel to, and intermediate, the edges as described above. This interleaving may result in at least two portions of a length of the cord being disposed on the outside of the reinforcement 301 and at least two portions thereof being disposed on the inside with alternate portions on the outside and the inside along the length. A single length may have between 2 and 250 portions disposed on the outside of the reinforcement 301 with a like number of portions being disposed on the inside thereof. The degree or extent of interleaving along a particular length may determine the number of interleaving lines or zones intermediate the edges.

As the number of portions increases, the lines or zones of interleaving may become less readily visible due to the overall black color of the rubber coated cord and/or the interleaving pattern. This may also occur when several cords are employed together in the formation of the reinforcement.

The cord may be associated with a green or unvulcanized rubber layer or belt. The reinforcement 301 may be produced by forming the cord in a zigzag pattern over the surface of such a rubber layer or belt. Also, a rubber layer may be placed over the outer surface, instead of, or together with, a second rubber layer on the inside. Rubber shoulder portions may be disposed adjacent the edges of the reinforcement 301 either with the cord(s) alone or in combination with one or more rubber layers. The shoulder portions may assist in the positioning of the reinforcement 301 with respect to the carcass 14 so that the edges will be properly disposed in the finished tire 10 in relation to the center portion. The shoulder portions may minimize the possibility of air entrapment during curing.

While the above description has been directed primarily to an endless reinforcement breaker for pneumatic tires it will be apparent that the present invention may be utilized to provide reinforcements with various layered constructions with the same or different dimensions or constructions in individual layers. Also, the present invention is useful for the production of other cord components of a tire, for example, for the carcass itself or for a unitized breaker/carcass assembly. The reinforcement can be wound over a carcass or applied thereto in flat band form and expanded, e.g., to produce a belted bias-ply tire or wound over or applied to an expanded carcass such as in the production of a radial-ply tire. Furthermore, the reinforcement can be used with a tire from which the tread has been removed, new tread stock applied and vulcanized to form a retread tire.

In accordance with the present invention, portions of endless reinforcements 301 are shown in FIGS. 3 and 4. The reinforcement 301 illustrated in FIG. 3 may be similar to the one shown in FIG. 4 except that the number of interleaving lines may be increased from 5 to 13. The angle of the cord(s) in each case may be approximately 30° and the width may be approximately 10.0 mm. However, it will be seen that the number of interleaving lines may change from one reinforcement to another. As shown in the figures, a cord may be positioned on a green rubber belt 100 with cord length 111 interleaved with cord lengths 112 to form an interleaving line or zone 113. Reversal points 114 at the edges of the reinforcement 301 may be seen from the figures.

As stated above, a single reinforcement 301 in accordance with the present invention may produce reduced weight with comparable performance in a tire 10. This single reinforcement 301 thus lightens the tire 10 with essentially no performance tradeoff, even though the complexities of the structure and behavior of the pneumatic tire are such that no complete and satisfactory theory has been propounded. Temple, Mechanics of Pneumatic Tires (2005). While the fundamentals of classical composite theory are easily seen in pneumatic tire mechanics, the additional complexity introduced by the many structural components of pneumatic tires readily complicates the problem of predicting tire performance. Mayni, Composite Effects on Tire Mechanics (2005). Additionally, because of the non-linear time, frequency, and temperature behaviors of polymers and rubber, analytical design of pneumatic tires is one of the most challenging and underappreciated engineering challenges in today's industry. Mayni.

A pneumatic tire has certain essential structural elements. United States Department of Transportation, Mechanics of Pneumatic Tires, pages 207-208 (1981). An important structural element is the belt, typically made up of many flexible, high modulus cords of natural textile, synthetic polymer, glass fiber, or fine hard drawn steel embedded in, and bonded to, a matrix of low modulus polymeric material, usually natural or synthetic rubber. Id. at 207 through 208.

The flexible, high modulus cords are usually disposed as two belts. Id. at 208. Tire manufacturers throughout the industry cannot agree or predict the effect of different twists of cords on noise characteristics, handling, durability, comfort, etc. in pneumatic tires, Mechanics of Pneumatic Tires, pages 80 through 85.

These complexities are demonstrated by the below table of the interrelationships between tire performance and tire components.

CARCASS LINER PLY BEAD/APEX BELT OV'LY TREAD MOLD TREADWEAR X X X NOISE X X X X X X HANDLING X X X X X X TRACTION X X DURABILITY X X X X X X X ROLL RESIST X X X X X RIDE X X X X COMFORT HIGH SPEED X X X X X X AIR X RETENTION MASS/ X X X X X X X WEIGHT

As seen in the table, crown reinforcement characteristics affect the other components of a pneumatic tire (i.e., belt affects carcass ply, overlay, bead/apex, etc.), leading to a number of components interrelating and interacting in such a way as to affect a group of functional properties (noise, handling, durability, comfort, high speed, and mass/weight), resulting in a completely unpredictable and complex composite. Thus, changing even one component can lead to directly improving or degrading as many as the above ten functional characteristics, as well as altering the interaction between that one component and as many as six other structural components. Each of those six interactions may thereby indirectly improve or degrade those ten functional characteristics. Whether each of these functional characteristics is improved, degraded, or unaffected, and by what amount, certainly would have been unpredictable without the experimentation and testing conducted by the inventors.

Thus, for example, when a belt structure of a pneumatic tire 10 is modified with the intent to improve one functional property of the pneumatic tire, any number of other functional properties may be unacceptably degraded. Furthermore, the interaction between the belt (e.g., bidirectional cords, etc.) and the carcass ply, overlay, tread, bead/apex may also unacceptably affect the functional properties of the pneumatic tire. A modification of the carcass ply may not even improve that one functional property because of these complex interrelationships.

Thus, as stated above, the complexity of the interrelationships of the multiple components makes the actual result of modification of a carcass ply, in accordance with the present invention, impossible to predict or foresee from the infinite possible results. Only through extensive experimentation has the single reinforcement 301 of the present invention been revealed as an excellent, unexpected, and unpredictable option for a complete belt structure.

The previous descriptive language is the best presently contemplated mode or modes of carrying out the present invention. This description is made for the purpose of illustrating an example of general principles of the present invention and should not be interpreted as limiting the present invention. The scope of the invention is best determined by reference to the appended claims. The reference numerals as depicted in the schematic drawings are the same as those referred to in the specification. For purposes of this application, the various examples illustrated in the figures each use a same reference numeral for similar components. The examples structures may employ similar components with variations in location or quantity thereby giving rise to alternative constructions in accordance with the present invention. 

What is claimed:
 1. A pneumatic tire comprising: a carcass reinforced by a carcass ply extending from a first bead to a second bead; and a single reinforcement disposed radially outward of the carcass ply in a crown portion of the pneumatic tire, the single reinforcement comprising a continuous cord forming a generally zig zag pattern across the width of the crown portion, the continuous cord being part of a continuous strip with a constant width of 3.0 mm to 30.0 mm.
 2. The pneumatic tire of claim 1 wherein the continuous cord has a 2×0.295 high tensile steel construction.
 3. The pneumatic tire of claim 1 wherein the continuous cord has a 2+2×0.22 ultra tensile steel construction.
 4. The pneumatic tire of claim 1 wherein the continuous cord is part of a group of cords of identical construction.
 5. The pneumatic tire of claim 1 wherein the continuous cord comprises carbon fiber.
 6. The pneumatic tire of claim 1 wherein the continuous cord comprises polyester.
 7. The pneumatic tire of claim 1 wherein the continuous cord comprises polyamide.
 8. The pneumatic tire of claim 1 wherein the continuous cord comprises aramid.
 9. The pneumatic tire of claim 1 wherein the continuous cord comprises fused polyester.
 10. A method for designing a pneumatic tire comprising: replacing a first belt, a second belt, and an overlay with a single continuous reinforcement, the single continuous reinforcement comprising the continuous cord being part of a continuous strip with a constant width of 3.0 mm to 30.0 mm. 